1. Field of the Invention
The present invention relates to antenna module designs and more particularly, to a multi-band HAC compatible antenna module, which has a metal shield mounted therein around the built-in antenna for resonant coupling with the antenna to lower electromagnetic interference and to provide HAC characteristic.
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2. Description of the Related Art
FCC (Federal Communications Commission) introduced new regulations regarding digital cellular telephones. In order not to interfere with concomitant use of a cellular telephone and hearing aids, cellular telephone providers are responsible to keep EMI (electromagnetic interference) below a certain level. Cellular telephone provides are also requested to prepare some types of cellular telephones for enabling audio signal to be transmitted to hearing aids by means of telcoil coupling.
FCC established the aforesaid regulations just because analog cellular telephones are being disappeared from the market FCC indicates no significant problems are found during the concomitant use of an analog cellular telephone and hearing aids.
With respect to the problem of concomitant use between cellular telephones and hearing aids, ANSI (American National Standards Institute) established compatibility between hearing aids and cellular telephone under “ANSI C63.19”.
Regular cell phone antennas cannot meet HAC (Hearing Aids Compatibility) standards. Therefore, HAC compatible cellular telephones are continuously created. US20060140428 discloses a mobile wireless communications device including an upper housing and a lower housing being slidably connected together for sliding between a retracted position and an extended use position.
US20070003088 discloses an electronic device including a ground plane with two opposed edges, an electrical component, and an electrical conductor coupling the electrical component to a point on the ground plane that is substantially spaced from each of the opposed edges. These methods are not applicable to antenna designs for straight cellular telephone for improving HAC characteristic.
The built-in antennas of regular straight cellular telephones show low performance in HAC. The HAC design of a single-pole antenna for straight cellular telephone does not have a reference ground plane, resulting in a high field strength at the reference location that is disposed near the antenna.